The first method for production of biodiesel is by pyrolysis reaction in which oils or fats are thermally cracked to similar chemical compositions of fossil fuels in the absence of oxygen (Ma and Hanna 1999). However, pyrolyzed vegetable oils are contaminated with trace amounts of sulfur, water, and sediment, and these could lead to corrosion problems in the engine. This process usually requires high main­tenance cost especially the distillation unit for various fractions separation (Ma and Hanna 1999). The removal of oxygen during the thermal processing of pyrolysis eliminates the benefits of using oxygenated fuel.

Another method for production of biodiesel is by microemulsion. It is defined as a colloidal equilibrium dispersion of optically isotropic fluid microstructures with dimensions generally 1-150 nm range formed spontaneously from two normally immiscible liquids and one or more ionic or nonionic amphiphiles (Schwab et al. 1987). Ionic and nonionic microemulsions of aqueous ethanol in soybean oil have good performances as diesel fuel oil. Emulsion of 53% (vol) alkali-refined and win­terized sunflower oil, 13.3% (vol) 190-proof ethanol, and 33.4% (vol) 1-butanol when undergoing 200 h laboratory screening endurance test, irregular injector nee­dle sticking, heavy carbon deposits, incomplete combustion, and an increase of lubricating oil viscosity were reported (Ziejewski et al. 1984).

Transesterification is the most widely used process producing biodiesel from vegetable oils. Transesterification is the alcoholysis of triglyceride esters, resulting
in a mixture of mono-alkyl esters and glycerol (Fukuda et al. 2001). This process has been used to reduce the viscosity of triglycerides and enhance the physical prop­erties of renewable fuels with the aim to improve the performance in engine (Clark et al. 1984). Transesterification can be carried out through a variety of ways in the presence of alkali catalyst, acid catalyst, biocatalyst, heterogeneous catalyst, or using alcohols under supercritical conditions without catalyst.

Microemulsions of vegetable oils would reduce the biofuel viscosity, but engine performance problems of injector coking and carbon deposits still persist (Bala 2005). Pyrolysis of triglycerides produces compounds with incompatible biodiesel quality in terms of ash, carbon residues, and pour point (Schwab et al. 1987). Among all the conversion methods, transesterification of vegetable oils is the most promising route to produce biofuel with similar properties and performances as hydrocarbon-based diesel fuels (Fukuda et al. 2001).

Enzymes are renewable. They can be cultivated from bacteria and fungi and be mass-produced. Enzymatic reactions typically have the characteristics shown in Table 11.1.

The enzymatic process is intrinsically “green,” especially in comparison with the chemical process. It can be applied to simultaneously convert both neutral oil

and FFA. Applying enzyme catalysts for biodiesel production has long been rec­ognized as a better approach to biofuel production. However, full development and successful application of enzymatic biodiesel technology are hampered by poisoning of the catalyst, which in turn leads to high costs and inefficient opera­tions. Poisoning or deactivation of the catalyst is due to methanol, ethanol and most especially glycerol. This problem has long puzzled scientists and research­ers, and the solution has not been known until the use of the right inert solvent in the reaction [ET Process®, patented worldwide, Sunho Biodiesel Corporation (SBC)] was discovered. Figure 11.1 shows the deactivation effect from glycerol droplets when inert solvent is slightly insufficient for a column reaction. Glycerol deactivation is independent of whether the operation is performed with a packed bed reactor or a CSTR. Without an inert solvent, the activity of the enzyme will gradually decrease within a period of time.

Macroalgae biomass can be converted by biological methods. Fermentation is a biological conversion method of the biomass to produce energy carriers like hydro­gen, ethanol and biogas. All living organisms obtain the energy necessary to sustain life, from the oxidation of organic substances by molecular oxygen, in the process of respiration. Under anaerobic conditions (low oxygen concentrations), many organisms, including yeast, obtain the energy from the process of fermentation. Fermentation normally occurs under anaerobic conditions but also occurs some­times when oxygen is present (Prescott et al. 2002).

In alcoholic fermentation, characteristic of many yeast species, the fermentation process starts with one molecule of the six carbon sugar and terminates with two molecules of the two-carbon alcohol-ethanol and two molecules of CO2. The major source for energy production in the yeast Saccharomyces cerevisiae (S. cerevisiae) is glucose.

Glycolysis is the general pathway for conversion of glucose to pyruvate, whereby production of energy in form of ATP is coupled to the generation of intermediates and reducing power in form of NADH for biosynthetic pathways (Fig. 13.1). Two principal modes of the use of pyruvate in further energy production can be distin­guished: respiration and fermentation. As the figure depicts, the input of anaerobic fermentation is sugar and the product of respiration is glycerol, ethanol, CO2 and succinate. The fermentation pathway is being utilised in bioethanol production (Feldmann 2005).

Yeast has been the main component in fermentation process. It converts complex material such as sugar to simpler material, that is, ethanol. S. cerevisiae is well — known yeast commonly used in fermentation and capable of galactose fermentation (Goh and Lee 2010). It is often used in research as a model eukaryotic organism because it is easy to manipulate and culture (Chen 2008). It is widely used in the fermentation industry such as wine, bread and beer production. It can withstand temperatures as low as 1-3% and as high as 40%. The optimum temperature for its growth will be 28%. S. cerevisiae can survive in extreme condition such as acidic condition (pH 3.0 or lower) (Presscott et al. 2002). Therefore, it is also known as extremophiles.

1.3.1 First-Generation Biofuels

For long-term sustainable biodiesel deployment, a vertical integration of palm bio­diesel production is required where the palm biodiesel plants are to be built in close vicinity to palm oil mills and palm oil refinery. The ultimate goal is the extraction and production of value-added products from palm biodiesel, i. e. palm phytonutri­ents such as carotenes, vitamin E, squalene and sterols, via fractional distillation and integrated approach. These phytonutrients can serve niche market for pharma­ceutical application. There will also be continued efforts in addressing sustainable/ environmental issues of palm biodiesel production concerning GHG emissions and indirect land use change.

5.2.3.1 Palm Kernel Shells

In the palm oil mill, after the hydrocyclone separation process, the palm nuts are sent to the crushing unit where they are dried and cracked, whilst the PPF are sent to the boiler. The cracked shells without the kernel or seeds are called palm kernel shells (PKS). PKS can be described as the hard endocarps surrounding the palm kernels or seeds which are obtained after the residual nuts from the screw press are mechanically crashed to extract the seeds or kernels.

Presently due to increase in palm oil production, the world’s annual generation of PKS is estimated at 11.1 million tonnes as compared to 2.52 million tonnes and

4.3 million tonnes in 2004 and 2006, respectively (MPOB 2012). Because PKS possess high solid content (with a calorific value of about 22.14 MJ/kg), low sul­phur (about 0.09% dry weight) and low ash (about 3% dry weight) contents, they are often used as fuel for the power plants in the palm oil industry (Yusoff 2006). However, nearly 40% of these wastes are utilised by the oil mill for power genera­tion; the rest are dumped in open space in the crushing unit and sometimes inciner­ated in an uncontrolled manner within the industry contributing to significant environmental pollution.

The proximate and ultimate compositional analyses carried out by Sukiran (2008) show that PKS contains about 30% moisture content by wet weight, 73.74% volatile matter, 18.37% fixed carbon, 2.21% ash, 53.78% carbon, 7.20% hydrogen and 36.30% oxygen. The inorganic composition of PKS expressed in % ash (mois­ture free) includes 2.96% Si2O, 0.60% K2O, 0.48% CaO, 0.83% MgO, 0.08% Fe2O3, 0.24% Al2O3 and 0.59% P2O5 (Chaiyaomporn and Chavalparit 2010). The fuel den­sity of PKS is about 1,430 kg/m3 (Mohammed et al. 2012).

The holocellulose compositions of PKS are about 20.8% cellulose and 22.7% hemicellulose with lignin content of about 50.7% (Saka 2005).

At the moment, almost all commercial biodiesel productions used homogeneous base catalysts. However, the major disadvantage of homogeneous catalyst is the fact that it cannot be reused. Furthermore, the separation of catalyst from the reaction mixture requires further stages of washing, and the process is usually conducted in batch type rather than continuous type. In recent times, the research focusing on using heterogeneous base catalysts becomes more extensive in order to find the catalyst that can contribute to an economical process. The utilization of heteroge­neous catalyst means that they can be placed in a fixed bed reactor and allows con­tinuous biodiesel production.

Alkaline metal oxides are receiving considerable attention in biodiesel synthesis, as they contain basic sites that can catalyze the reaction. Examples of alkaline metal oxide catalysts are calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), and magnesium oxide (MgO). CaO is one of the most established alkaline metal oxide catalyst used, owing to its relatively high basic strength and high avail­ability. It also holds the advantages of easy product recovery and easier handling as compared to NaOH and KOH.

A study on different kinds of metal oxides was conducted by Kawashima et al. (2008) for obtaining biodiesel using heterogeneous base catalysts. The catalysts were prepared from different types of metal oxides including calcium, barium, mag­nesium, and lanthanum. Among these, calcium-containing catalysts showed high yields of methyl ester. It is proposed that the weaker base strengths of Ba, Mg, and La series resulted in low activity for the transesterification reaction.

Liu et al. (2008) conducted the transesterification of soybean oil catalyzed by CaO. The biodiesel yield exceeded 95% for 3 h reaction time. Its lifetime was found to be better than K2CO3 and KF loaded on y-Al2O3 and maintained its catalytic activ­ity even after being used for 20 cycles, with only minimal reduction of biodiesel yield. The author suggested that the catalyst requires some amount of water for the reaction rate of transesterification to progress effectively, in this case was 2.03% of water content.

Calcium compounds were used as solid base catalysts in conversion of soybean oil into biodiesel (Kouzu et al. 2008). From the results, CaO resulted in the highest yield of FAME with the shortest time, followed by calcium hydroxide (Ca(OH)2), while calcium carbonate (CaCO)) seemed to be inactive for catalyzing the trans­esterification. It was found that CaO was deactivated when exposed to air. CO2 and moisture adsorbed on the basic sites of CaO rendered the catalyst and decreased its catalytic ability, based on the FAME yield.

Various attempts have been made to further increase the efficiency of CaO as heterogeneous base catalyst in biodiesel synthesis. One of the works was done by Yan et al. (2009). Lanthanum modified CaO catalysts were prepared for the trans­esterification process. The catalyst Ca3La1, defined by the molar ratio of La to Ca, successfully produced 94.3% FAME within 60 min at 58°C. The catalytic activity of the catalyst was comparable to NaOH in terms of FAME yield and even better than the other two catalysts (CajLa0 and Ca)La1). Furthermore, the mixed CaO — La2O3 catalyst is highly tolerable towards the fFa and water content in the feed­stock used.

Another attempt to improve the activity of CaO was done by Taufiq-Yap et al. (2011). CaO-MgO catalysts were synthesized using different Ca/Mg atomic ratios. The catalyst with the Ca/Mg atomic ratio of 0.5 (CM0.5) managed to obtain the highest biodiesel yield (90%), and the yield dropped as the Ca/Mg ratio increased. The author suggested that the decreased in the catalytic activity was caused by the low catalysts’ surface area. Higher loading above 0.5 at.% triggered the diffusion limitation between the reactant and the basic active sites. In addition, when CM0.5 was used, the FAME yield did not reduced significantly even after the fourth cycle.

The search for the efficient catalyst for biodiesel production is continued with the recent interest of catalyst made from cheaper source. The use of natural calcium sources for conversion of oils into biodiesel underlines the effort to cut down the cost of catalyst without affecting their catalytic performance.

The utilization of this type of catalyst adds value to the recycled waste, aside from being environmental friendly and green. The sources for the catalyst prepara­tion are presented in Table 9.3. Calcination step is essential for the decomposition of CaCO3-rich sources into CaO, which is the common heterogeneous base catalyst available. The process is conducted for several hours at high temperature to ensure that the catalyst prepared is viable for the biodiesel synthesis later.

Wei et al. (2009) investigated the use of egg shell for the transesterification of soybean oil. The author reported that the catalyst can be repeatedly used for 13 times without significant reduction in biodiesel yield and completely deactivates after being used more than 17 times. The study on the calcination temperature showed that biodiesel yield of 97-99% was achieved when the egg shell was calcined above 800°C, and the calcination below 600°C did not lead to the forma­tion of CaO.

Biodiesel was produced through transesterification of soybean catalyzed by combusted oyster shell (Nakatani et al. 2009). The process produced 73.8% of bio­diesel yield at optimum conditions, and it is comparable with the yield using CaO. Furthermore, the biodiesel purity was also quite high (98.4 wt%). Hu et al. (2011) synthesized catalyst from freshwater mussel shell, and biodiesel yield above 90% was achieved in 1.5 h reaction time. The author pointed out that the reduction of the catalytic activity was caused by the transformation of the catalyst into Ca(OH)2 and that the activity can be recovered after calcination in air at 600°C.

In cross-linking, intermolecular linkages are formed between enzyme molecules by means of bifunctional or multifunctional reagents such as glutaraldehyde, bisdiazo — benzidine, and hexamethylene diisocyanate. In cross-linking, the immobilized lipase is stable due to the strong interactions among enzyme and cross-linking agent. The application of this biocatalyst in biodiesel gives considerable good yield, but the small size of these aggregates creates problem during reuse (Cao et al. 2003; Andrade and Hlady 1986).

12.3.1.2 Entrapment

Entrapment of lipase entails capture of the lipase within a matrix of a polymer. Benefits of entrapment include cheap, fast, and easy procedure with mild operating conditions. Entrapped lipase is more stable than the physically adsorbed ones.

Application of entrapped lipase in biodiesel production has given average yields. This is due to the mass transfer limitations of entrapped lipase and erosion of enzyme from the surface of the support (Xavier et al. 1990; Trevan 1988).

12.3.1.3 Encapsulation

In this method of immobilization, the lipase is retained inside within a porous mem­brane forming a bilayered system. Direct contact between the enzyme and the sub­strates can be avoided in encapsulation. Enzyme leakage can be reduced due to the less leaching out of enzyme molecules from the matrix. When applied for produc­tion of biodiesel, encapsulated lipase has shown to give very low yields. This is due to the strong mass transfer limitations of encapsulated enzyme and clogging of pores with the substrate and product molecules (Yadav and Jadhav 2005).

12.3.1.4 Hybrid Immobilization Techniques

A combination of two or more of the above-mentioned techniques results in “hybrid immobilization.” This technique has given good results on industrial scale to food and pharmaceutical industry. Now this approach is being applied for transesterifica­tion reactions, and the results are quite promising (Bonrath et al. 2002). So this approach looks better in designing an efficient biocatalyst for biofuel industry.

Each microalgae strain responds differently to CO2 concentration. Thus, the period of time that the CO2 concentration must be maintained in a medium culture depends on microalgal species. The two-stage growth technique (Suali and Sarbatly 2012) can be applied to increase the CO2 utilization of microalgae specifically during the

second stage by using up to 30% of CO2 and <10% of dissolved oxygen (DO) in media culture with a dispersion rate between 10 and 40% (Fabregas et al. 2001), whereas 20% of DO in air for aeration decreased the photosynthesis and lipid pro­ductivity of microalgae (Ota et al. 2011).

High CO2 concentrations can be utilized during the second-stage culture period to increase the lipid or oil production of microalgae. The productivity can be increased by adding as little as 2% of CO2 (Chiu et al. 2009). It is important to note that CO2 utilization by microalgae only occurs in the presence of light. Thus, excess CO2 that was not utilized during the photosynthesis could have an adverse effect on the productivity of the microalgae. By using light illumination as low as 25 pmol m-2 s-1, an aeration rate of 1 L min-1, and 5% CO2, biomass can be pro­duced that is 63% lipids (Illman et al. 2001). When cultivated in the range of 6-8% of CO2, the biomass yield can be as much as 0.376 g L-1 d-1, whereas 9-10% of CO2 resulted in a lower biomass yield of 0.15 g L-1 d-1 (Ghirardi et al. 2000; Metzger and Largeau 2005). A summary of first — and second-stage operating conditions is pro­vided in Table 14.2.

Suzana Yusup, Murni Melati Ahmad, Anita Ramli, Khan Zakir, and Mas Fatiha Mohamad

Abstract This chapter highlights the potential of utilising biomass as a renewable feedstock to produce biofuel and biochemical. Technologies for the conversion pro­cesses are discussed. In addition, case study on biomass conversion to H2 is pre­sented. The effect of steam and newly developed bimetallic catalyst (Fe/Ni/ Zeolite-P) on palm oil wastes including palm shell (PS) and palm oil fronds (POF) decomposition for H2 production was experimentally investigated in thermogravi­metric analysis-gas chromatography (TGA-GC). Presence of steam increased the H2 content by 28% for both palm oil wastes. Maximum H2 content in the product gas generated was 64 mol% from PS for the catalytic steam gasification. On the other hand, for POF maximum H2 content of 50-mol% is observed in the product gas. Palm wastes can be a potential feedstock for H2 production utilising catalytic steam gasification process and can contribute to considerable renewable and clean energy for future.

Keywords Biomass conversion • Fuel • Solid • Liquid • Gaseous

S. Yusup (*) • M. M. Ahmad

Chemical Engineering Department, Green Technology Mission Oriented Research,

Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh, Perak 31750, Malaysia e-mail: drsuzana_yusuf@petronas. com. my

A. Ramli

Fundamental and Applied Science Department, Green Technology Mission Oriented Research, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh, Perak 31750, Malaysia

K. Zakir • M. F. Mohamad

Biomass Processing Laboratory, Green Technology MOR, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh, Perak 31750, Malaysia

R. Pogaku and R. Hj. Sarbatly (eds.), Advances in Biofuels,

DOI 10.1007/978-1-4614-6249-1_3, © Springer Science+Business Media New York 2013

3.1 Introduction

Energy is a fundamental enabler of the economy. The challenges to come are vast utilisation of renewable energy; at the same time the sources of the renewable energy should avoid food versus fuel crisis. This prompted diversity of primary raw materials for manufacturing renewable transportation fuel that includes waste and recycled materials. Table 3.1 shows the relative importance of solid fuels where industrialisation was founded largely on fuels (Tillman 1991). Total fuel consump­tion is about 76.4 quad. Btu in which biomass is the secondary source to coal as the feedstock. In Malaysia, biomass contributes about 0.5% of fuel used to support the industrial sector (Evald and Majidi 2003).

Preparation of activated carbon from EFB by microwave-assisted KOH activation for methylene blue adsorption (Foo and Hameed 2011), PKS by phosphoric acid impregnation (Lim et al. 2010), PKS by ZnCl2 and physical activation for methane adsorption (Arami-Niya et al. 2010; Abbas and Daud 2009), PKS to remove lead ions from aqueous solutions (Issabayeva et al. 2006), PKS for basic dye adsorption (Jumasiah et al. 2006), OPT by phosphoric acid impregnation (Hussein et al. 2001), PKS by chemical activation with K2CO3 (Adinata et al. 2007) and PKS by ZnCl2 impregnation for the removal and recovery of residual oil from POME (Ngarmkam et al. 2011) have been reported. The results from Arami-Niya et al. (2010) indicated a significant increase in methane adsorption after physico-chemical activation. Preparation of palm oil empty fruit bunch-based activated carbon for removal of 2,4,6-trichlorophenol has also proven feasible (Hameed et al. 2009). Catalytic char­acteristics of activated carbon manufactured from PKS for methane decomposition were studied using a thermobalance (Abbas and Daud 2009).

The development of microporosity for the oil-palm-shell activated carbon would lead to potential applications in gas-phase adsorption for the removal of air pollut­ants (Guo and Lua 2002) . Tan and Ani (2004) utilised PKS to prepare carbon molecular sieve (CMS) by carbonisation for air separation and concluded that PKS is a highly potential material for CMS. Other studies (Ahmad et al. 2008; Adinata et al. 2007; Sumathi et al. 2010) have also utilised PKS and other OPW as activated carbon for gas removal. Some other applications of OPW for carbon materials include high porosity carbon powder from OPW as an adsorbent (Alam et al. 2009; Tan et al. 2010), carbon glassy from PKS for electrodes (Aroua et al. 2008), green nanoparticles from POME (Gan et al. 2012) and electrical carbon brushes as conductors.